II - DCE FEL ČVUT v Praze

SIMATIC S7 HART Analog Modules
Analog values and
resolution
4-16
The representation of the analog values is the same as for the analog input
module SM 331; AI 4 x 0/4...20mA, see Section 3.1.2. The resolution of the
measured value is directly dependent on the selected integration time, i.e. the
greater the integration time selected for an analog input channel, the more
precise the resolution of the measured value.
10 bits + polarity (integration time 2.5 ms)
13 bits + polarity (integration time 16.6/ 20 ms)
15 bits + polarity (integration time 100 ms)
Table 4-9 Output range of the analog input modules SM 331; AI 2 x 0/4...20 mA HART
Selected output type Explanation Output range
Current The digitalized analog values can be found in part 3.1.2 in Table
3-4 of the current measuring range.
Integration times
when HART is
used
Default settings
Wire break
monitoring
Inserting and
removing modules
Operation with
standard master
0 to 20 mA
4 to 20 mA
If you use measuring transducers with the HART protocol, it is advisable to
assign integration times of 16.6, 20 or 100 ms, in order to minimize the
influence of the modulating alternating current on the measuring signal.
The HART measurement mode is set as default. There are other default
settings for integration time, diagnostics, interrupts (see Table 4-4). The
HART analog module uses these settings, unless you modify them using
STEP 7.
Wire break monitoring is not possible for the current range 0 to 20 mA.
For the current range 4 to 20 mA, if the input current falls below I3.6
mA this is interpreted as a wire break and a diagnostic interrupt is
triggered (provided the interrupt is enabled).
The HART analog modules support the function “Change modules during
operation.” However, it is only possible to evaluate the insert / remove
module interrupts with a S7/M7 400 CPU master and an active backplane bus
in the ET 200M.
Information on operating the modules in a distributed configuration with a
standard master can be found in manual /140/. The manual lists the
differences to be taken into consideration if you are operating the modules
with a S7/M7 DP master and a standard master (for example, IM 308C with
S5).
Parameter assignment with COM PROFIBUS (.GSE file or type file
required)
Restricted evaluation when inserting or removing modules.
I/O Modules with Intrinsically-Safe Signals
C79000-G7076-C152-04